Attention-related modulation in the superior colliculus encodes perceptual sensitivity, but not perceptual choice

Neurons in the superior colliculus (SC), like those in cortex, are modulated by shifts in attention but contribute differently from visual cortex neurons. It remains debated whether SC attention-related activity represents enhanced perceptual sensitivity, decision criterion shifts, or motor bias linked to saccade planning at neurons' response fields. We dissociated these components by independently controlling behavioral sensitivity, perceptual decision criterion, and motor response criterion in a visual spatial attention task in two male rhesus monkeys. SC activity correlated strongly with behavioral sensitivity and motor criterion for selecting a saccade target within the response field, independent of saccade execution. In contrast, SC responses remained unchanged despite large shifts in decision criterion when motor bias was excluded. Notably, SC activity did not predict trial-by-trial choice accuracy. These results demonstrate that the SC specifically supports components of attention related to heightened perceptual sensitivity and response selection, while being largely independent of internal perceptual decision criterion and trial outcome.